European Patent Publication No. 0 474 904 A1 discloses a commutator gear drive unit for the window lift drive of a motor vehicle wherein the motor shaft of the commutator motor is connected to a wormshaft of the gear unit and the commutator of the commutator motor is mounted in brush socket parts for the brush holder which are molded integrally on a flat conductor plate. The flat conductor plate has several structural elements serving to control the commutator motor, including two motor relays which serve to energize the motor winding for the following motor states: "resting", "turning right" and "turning left".
The motor relays take up a considerable amount of space on the conductor plate and thus substantially affect the structural size of the complete control unit. Owing to their close proximity to the electronic components of the conductor plate, electrical breakdowns may result from the switching processes of the motor relays. Accordingly, additional casings or circuitry are required which lead to a further increase in the structural size of the drive unit.
Relays having a tri-stable behaviour for controlling commutator motors for the motor states "resting", "turning right" and "turning left" are known. German Patent No. 32 43 266 C2 discloses a polarized relay which consists of two first yokes which have a U-shaped cross-section which are positioned with their short arms facing each other. The polarized relay also includes second smaller yokes which are enclosed at a distance by the first yokes. A permanent magnet having a magnetic axis running at right angles to the large faces the yokes is mounted between the first and second yokes. The second yokes furthermore enclose an exciter coil which encloses a rod-like armature which is displaceable in the direction of coil axis. The rod-like armature has two ends lying outside of the exciter coil which are formed as plates which are displaceable between the inner faces of the short arms of the first yokes forming pole faces, and the end faces of the second yokes.
The armature consists of two rod halves divided radially in the center of the exciter coil and between which a coil compression spring is mounted whose pretension is measured so that the plates of the armature in the current-less state of the exciter coil adjoin the pole faces of the short arms of of the armature in the current-less state of the exciter coil adjoin the pole faces of the short arms of the first yokes, whereas in the current-charged state of the exciter coil, one or the other plate adjoins the corresponding end faces of the second yokes, depending on the direction of the current flow.
German Patent Publication No. 35 46 382-A1 discloses a polarized electrical mini-relay which is designed as a two-way reverser relay. A leaf armature and reflux elements are mounted at each of the two free ends of a coil core. The leaf armatures are held by permanent magnets arranged in series and during excitation of the coil carry out a synchronized switching process.